Hydraulic control system for concrete placer

ABSTRACT

A concrete pumping apparatus having a pair of fluid rams cooperating with conduits for delivering material through the conduits by supplying pressured fluid from a hydraulic control circuit to the rams. The hydraulic control circuit includes a pump delivering fluid to the rams at varying flow rates and pressures with a member in the pump positionable to a plurality of positions to adjust the flow rate of the fluid. The member is adjustable by a manual control means and automatic compensator means communicating with the output of the pump with an element of the compensator means positioned as a function of the pressure of fluid from the pump. A linkage means is interposed between the element and the member to move the member at varying inclements as the pressure of fluid is increased.

United States Patent 1 Schaible, deceased et al. 1 Jan. 16, 1973 [54]HYDRAULIC CONTROL SYSTEM FOR 3,429,123 2/1969 Burroughs ..60/52 vsCONCRETE PLACER [75] Inventors: Aaron M. Schaihle, deceased, late of gfzifs ty kfi: k l

gf zj pl i' i firj f', AztorneyDressler, Goldsmith, Clement & Gordon 9 9Waterford; Harry W. Davidson, [57] ABSTRACT Burlington, both of Wis. I Aconcrete pumping apparatus having a pair of fluid [73] Asslgnee: CaseCompany rams cooperating with conduits for delivering material [22]Filed: Jan. 11, 1971 through the conduits by supplying pressured fluidfrom a hydraulic control circuit to the rams. The PP N03 105,265hydraulic control circuit includes a pump delivering fluid to the ramsat varying flow rates and pressures 52 U.S. Cl ..417/342 with a memberin the Pump positionable a plurality [51] Int. Cl ..F04b 9/08 of psitinsadjust the flow rate of the fluid- The [58] Field of Search ..417 342900- 60/52 vs member is adjustable by a manual means and automaticcompensator means communicating with [56] Reerences Cited the output ofthe pump with an element of the compensator means positioned as afunction of the pres- UNITED STATES PATENTS sure of fluid from the pump.A linkage means is interposed between the element and the member to moveS fi I the member at varying inclements as the pressure of i 7 OITC e a.

fluid is increased.

1 1 Claims, 4 Drawing Figures PATENTEUJAN 16 I975 PS I SHEET 1 [IF 2 fsisi i l E 1 i 5 l I 50 2 20 10 5 HYDRAULIC CONTROL SYSTEM FOR CONCRETEPLACER The present invention relates generally to concrete placementapparatus and more particularly an improved hydraulic control system forcontrolling the rate of flow in response to changes in pressure of thefluid.

One type of concrete placement apparatus which has found a remarkabledegree of commercial success includes a pumping unit in which a pair offluid rams cooperate with a pair of pistons slidable in conduits.Pressured fluid is supplied to the rams to reciprocate the pistons andmove fluent material, such as concrete, to a common outlet where it isdelivered to a job site. In order to increase the versatility of a unitof this type, extremely long conduits are utilized so that the pumpingunit may be placed in one location and concrete may be delivered toanyone of a plurality of locations. Pumping units of this type are shownin U.S. Pat. Nos. Re. 26,820; 3,327,641; and 3,425,356.

SUMMARY OF THE INVENTION The present invention relates specifically to ahydraulic control system for supplying pressured fluid to a concreteplacement unit of the type disclosed in Pat. No. 3,494,290, assigned tothe assignee of the present application.

According to the present invention, a pressure compensating mechanism isincorporated into the hydraulic control and automatically reduces theoutput flow of a pump as the pressure increases beyond a predeterminedlimit.

More specifically, the present invention contemplates a hydrauliccontrol circuit for a concrete placement apparatus which has first andsecond fluid rams cooperating with pistons reciprocated in conduits todeliver a continuous supply of material through a single outlet conduit.The control mechanism includes a pump having a servo-stem or membermovable to a plurality of positions to define various flow rates for thepump. The member is movable to anyone of a plurality of positions by amanual control means and automatic pressure compensating means cooperatewith the member to correspondingly reduce the output flow of the pump asthe pressure exceeds a corresponding predetermined limit.

The pressure compensating means is in the form of an elementreciprocable within a chamber and biased to a first position with oneend of the chamber in communication with the outlet for the pump. As thepressure of fluid increases, the element is moved from the firstposition to automatically move the member to a corresponding reducedflow rate.

According to one aspect of the present invention, the pressurecompensating means incorporates linkage means between the element andthe member which is in the form of a bell crank having first and secondangularly related links, each of which defines an effective moment armrespectively for the element and the member. The ratio between themoment arm for the member and the element progressively increases as theelement is moved from a first position so that the member is moved inprogressively increasing increments for each increment of movement fromthe first position of the element. The particular arrangement allows formore efficient operation of the entire unit and results in more accuratecontrol in flow rates as the pressure increases.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS FIG. 1 is afragmentary schematic view of the hydraulic control circuit as well as aportion of the concrete placement system;

FIG. 2 is an enlarged plan view of the compensating means forming partof the hydraulic control circuit;

FIG. 3 is a view, partly in section, taken generally along line 3-3 ofFIG. 2; and

FIG. 4 (appearing with FIG. 1) is a graph showing the pressure versusthe flow rate of fluid from the pump controlled by the linkage ofthepresent invention.

DETAILED DESCRIPTION While this invention is susceptible of embodimentin many different forms, there is shown in the drawings and will hereinbe described in detail one specific embodiment, with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit theinvention to the embodiment illustrated.

A concrete pumping apparatus for which the present invention is A,particularly adapted is schematically shown in FIG. 1 and is generallydesignated by the reference numeral 10. The concrete pumping apparatusincludes a concrete placement conduit 12 which receives material from aconcrete pumping unit 14 for delivery to a work site through anarticulated boom (not shown) supporting a further conduit (not shown).Since the articulated boom and the conduit cooperating with the boomform no part of the present invention and are disclosed and claimed inco-pending application Ser. No. 105,266, filed Jan. ll, 1971, nodetailed description thereof appears to be necessary.

The concrete pumping unit 14 for delivering material to conduit 12 isschematically illustrated in FIG. 1 and includes first and seconddelivery lines 20 and 22 respectively having pistons 24 and 25reciprocated therein. The conduits 20 and 22 communicate with theplacement conduit 12 at their outer ends and also are in communicationwith the source of concrete (not shown) through conduits 26 and 28 withvalves in the respective conduits 26 and 28. The conduits 20 and 22 alsohave valves 30 and 32 in communication therewith. The respective valvesare selectively actuatable to place one of the conduits 20 or 22 incommunication with the concrete source while placing the other of theconduits in communication with the outlet conduit 12. As more clearlyset forth in the above mentioned Pat. No. 3,494,290, as piston 24 isbeing moved forwardly, control valve 30 is open while control valve inconduit 26 is closed so that concrete material within conduit 20 isbeing delivered to the placement conduit 12. At this time, valve 32 inconduit 22 'is closed while the valve in conduit 28 is open and theretraction of the right-hand piston 25 will draw concrete from thesource (not shown) into the conduit 22 for subsequent delivery to themain placement line 12.

The reciprocation of the respective pistons is accomplished throughfirst and second fluid rams 40 and 42 respectively having piston and rodassemblies 44 and 45 reciprocated therein and connected to therespective pistons 24 and 25. The pressured fluid is supplied from areservoir or source 46 through a pump 48, a conduit 50, a control valve52 and conduits 54- and 56 to the head ends of the respective fluid rams40 and 42. The two position control valve 52 is adapted to supply fluidthrough one of the conduits 54 or 56 while connecting the oppositeconduit to the reservoir 46. The rod ends of of the respective cylindersforming part of the fluid rams 40 and 42 are interconnected by a singleconduit 58 so that one of the pistons will be extending while the secondpiston is being retracted.

According to the present invention, the hydraulic control circuitfurther includes manual means for adjusting the flow rate of the pumpand automatic pressure compensating means for adjusting the flow rate ofthe pump as a function of the pressure of the fluid to decrease the flowrate when the pressure exceeds a predetermined level.

Referring particularly to FIGS. 2 and 3 of the drawings, the pump 48,which may be of the commercially available type manufactured and sold byVickers Division of Sperry Rand, Troy, Mich., under the designationPVC45-l0 has a servo stem 60 incorporated therein. The servo stem ormember is positionable to a plurality of positions to adjust the flowrate of fluid from the pump.

The automatic compensating means cooperates with the stem or member 60and includes a cylinder 62 having an element or piston and rod assembly64 reciprocated within a chamber 66. The element 64 is normally biasedto a first position by biasing means or spring 68 which has a constantspring rate while the chamber 66 is in fluid communication with theoutlet of the pump through a branch conduit 69 (See FIG. I). Thecylinder is supported by a trunnion mounting 70 having a bolt 72extending through a support plate 74 secured to the pump 48 so that thecylinder can pivot r relative to the support for a purpose to bedescribed later.

In the illustrated embodiment, the element 64 includes a rod 64a havingan enlarged portion or piston 64b secured to one end thereof by a pin640. The rod extends through an end cap 76 threaded on one end of thecylinder 62 to enclose the chamber 66 and a drain opening 77 is locatedon one side of the piston to drain any fluid which leaks past thepiston.

Thus, as the pressure of the fluid increases, the force of the fluidacts on the free end of piston 64b to move the element 64 against thebias of the spring 68 from the first position shown in FIG. 3.

The opposite or free end of the element 64 is connected through linkagemeans 80 to the member 60 to move the member 60 at varying increments asthe pressure of the fluid in conduit 50 is increased. For this purpose,the linkage means 80 includes a bell crank having a hub 81 supportingfirst and second links 82 and 84 which are angularly related to eachother and the hub 81 is rotatable on a pin 85 extending from plate 74.The link 82 is pivotally connected to the element 64 while the otherlink 84 cooperates with the member through a linkage 86. As is shown inFIGS. 2 and 3, the linkage 86 includes a first pair of links 88 pivotedintermediate their ends at 90 on an arm 92 extending from the supportplate 74 while the opposite ends of the links 88 are connected through afurther link or arm 96 to the link 84. An inspection of FIGS. 2 and 3will show that the member or servo stem 60 is moved through the linkagemeans as a function of the movement of the element 64. I

The pump 48 is designed such that a ten pound force will be acting onthe member 60 tending to move the element outwardly to a no-flowcondition at any time the pressure of the fluid from a pump exceeds alower minimum limit, such as 350 PSI. This force, tending to return themember 60 to a no-flow condition, is at all times acting upon thelinkage system including links 88, 96 and the bell crank.

The force from the pump, having a tendency to return the linkage to ano-flow condition, will tend to pivot the bell crank in a clockwisedirection, as viewed in FIG. 3, whenever the force from the fluid inchamber 66 exceeds the force exerted by the spring 68.

According to a prime aspect of the present invention, the angularlyrelated links 82 and 84 are positioned on the hub 81 to define effectivemoment arms about the pivot for the element 64 and the member 60. Thelinks are arranged so that the ratio of the respective moment armsdefined by links 84 and 82 respectively, is progressively increased asthe element 64 is moved from the first position. Stated another way,with particular reference to FIGS. 2 and 3, in which the pump 48 and thecompensating mechanisms are illustrated for a maximum flow condition forthe pump, a constant output flow will be realized from the pump untilsuch time as the pressure of the fluid is sufficient to overcome theforce of the spring 68.

When the element 64 begins to move from its first position, shown inFIG. 3, the bell crank will be pivoted in a clockwise direction. Thepivotal connection 99 between the element 64 and the link 82, as well asthe pivotal mounting of the cylinder 62 and the angular relation of thelink 82 on the hub 81, will result in a decrease in the effective momentarm for the element 64 about pivot 85 as the element is moved from thefirst position.

According to a further aspect of the present invention, the linkagesystem is arranged such that the effective moment arm of the element orpiston 64, defined by link 82, about pivot axis 85, is greater than theeffective moment arm for the member 60, defined by link 84 about pivotaxis 85 during the first stages of movement of the element 64 againstthe bias of the spring 68. However, during the latter stages ofmovement, i.e. when the element is approaching the fully extendedposition relative to the cylinder 62, the effective moment arm definedby link 82 is less than the effective moment arm defined by link 84.This is accomplished by arranging the links 82 and 84 at an anglerelative to the hub of bell crank 80 in the manner generally shown inFIG. 3. Stated another way, the effective moment arms for the member 60and the element 64 about the pivot 85 have a progressively increasingratio as the element 64 is moved from its first position. An example ofthe comparison of the moment arms, expressed in inches, is shown in thefollowing table where A is the effective moment arm for the piston orelement 64 while B is the effective moment arm for the element 60 aboutthe pivot axis 85.

% of travel of 64 Ratio This arrangement will result in having a greaterincrement of movement of element 64 per increment of pressure change asthe pressure in the system is increased. This is graphically illustratedin FIG. 4 where a line 200 is a plot of pressure of the fluid, inP.S.l., within the system versus the flow rate of the fluid, in G.P.M.,from the pump 48. A comparison of the line 200 with a line 202,indicating the pressure vs. flow rate plot of the fluid for a systemwhere the effective mo ment arms are equal reveals that the linkagearrangement of the present invention allows for more effective use ofthe maximum horsepower available from the power plant for operating thepump, which is shown by the line designated as 204 in the graph of FIG.4. For example, operating at 1,800 P.S.l. pressure, the maximum flow fora straight line linkage between the pump control member 60 and thecompensator element 64 will be approximately 19 gallons per minute whilethe flow for a linkage system wherein the effective moment arms define aprogressively increasing ratio will be on the order of 35 gallons perminute. Viewing the chart again, it will be noted that there are onlysmall increments of change of flow rate during approximately the firsthalf of pressure compensation while there would be a considerable.amount of change of flow during the latter half of pressurecompensation, i.e. when the pressure is controlled between 1,300 and2,000 P.S.I. Thus, up to approximately 1,700 P.S.l. pressure in thesystem, the pressure vs. flow rate curve 200 is approximately a straightline which parallels the maximum horsepower curve 204. However, once thepressure of the system exceeds 1,700 P.S.I., the curve 200 begins todrop off sharply so as to have a greater change in flow rate for equalincrements of pressure change. This arrangement allows for much moreaccurate control of the flow rate at higher pressures.

The control system of the present invention further includes manualcontrol means for setting the flow rate of the output pump. The manualcontrol means is in the form of a link 100 having an elongated slot 102receiving a pin 104 which is carried by the link 84 at a location spacedfrom the pivotal connection for link 96. The slot 102 and pin 104 definea lost motion connection between the bell crank and the link 100 withthe lost motion connection accommodating relative movement of the twolinks 84 and 100 when the pressure of the fluid in the system exceeds apredetermined level for the flow rate set by the manual control. Theslot 102 is of sufficient length to allow the pressure compensatingmeans to move the element 60 to a fully extended or no-flow conditionfrom the maximum flow condition shown in FIG. 2.

The manual control means 100 can be utilized to set any flow rate forthe pump and the compensating means will automatically reduce the flowrate when the pressure in the system exceeds the pressure correspondingto the flow rate set by the manual member 100. For example, if the flowrate were set at 30 G.P.M.

by pivoting the bell crank clockwise and compressing the spring 68, bymovement of the element 64, the pressure of the fluid in the system willhave to exceed approximately 1,875 P.S.l. before the force of the fluidon the element will exceed the opposing force of the spring 68.

According to another aspect of the invention, the length of the link 82is formed in two portions which are held' together by a bolt 111 so thatthe length thereof can readily be adjusted.

The automatic pressure compensating means of the present inventionprovides for an accurate control of the flow rate from the pump andautomatically overcomes the manual setting when additional hydraulicpower is needed to move concrete under extremely adverse conditions.Furthermore, the system can readily be incorporated into existingpumping equipment without any major modifications of the existingsystem. An inspection of FIGS. 2 and 3 reveals that the entire unit iscarried by the single plate 74, which can readily be attached at anappropriate location on existing equipment.

We claim:

1. In a concrete pumping apparatus having a concrete placement conduit,first and second fluid rams cooperating with said conduit for deliveringmaterial through said conduit, a hydraulic control circuit for supplyingpressured fluid to said rams comprising a pump delivering fluid to saidrams at varying flow rates and pressures, said pump having a memberpositionable to a plurality of positions to adjust the flow rate of saidfluid; automatic compensator means communicating with the outlet of saidpump and having an element positioned as a function of the pressure ofsaid fluid from said pump; and linkage means interconnecting saidelement and member, said linkage means moving said member at varyingincrements per increment of pressure of the fluid as the pressurev offluid is increased.

2. A concrete pumping apparatus as defined in claim 1 in which saidcompensator means includes a cylinder having said element reciprocatedtherein; and biasing means normally maintaining said element in a firstposition with the pressure of said fluid moving said element from saidfirst position.

3. A concrete pumping apparatus as defined in claim 2, in which saidbiasing means comprises a spring having a constant spring rate.

4. A concrete pumping apparatus as defined in claim 1, in which saidlast means includes linkage means between said element and said member.

5. A concrete pumping apparatus as defined in claim 4, in which saidlinkage means includes a bell crank having angularly related links withone link cooperating with said element and a second link cooperatingwith said member.

6. A concrete pumping apparatus as defined in claim 5, in which saidlinks define varying effective moment arms for said element and saidmember and in which the effective moment arm for said element decreasesas said element is moved from a first position.

7. A concrete pumping apparatus as defined in claim 1, and furtherincluding manual means cooperating with said last means for adjustingsaid member to define a predetermined flow rate for said fluid.

8. A concrete pumping apparatus as defined in claim 7, in which saidmanual means and said last means includes a lost motion connection toaccommodate relative movement when the pressure of fluid exceeds apredetermined level for said predetermined flow rate.

9. A concrete pump as defined in claim 1, in which said last meansincludes a bell crank pivoted about an axis with a first linkcooperating with said member and a second link cooperating with saidelement, said links being arranged to define effective moment arms forsaid member and said element which have a progressively increasing ratioas said element is moved from a first position.

10. In a concrete pumping apparatus having a pair of rams, eachcooperating with a piston reciprocated in a delivery line to delivermaterial to a placement conduit, a hydraulic control circuit including areservoir; a pump supplying fluid from said reservoir to said rams, saidpump having a member movable to a plurality of positions to adjust theflow rate of fluid from said pump; manual control means for adjustingsaid member to set various maximums of flow rate for said pump;compensator means for automatically adjusting said member as a functionof the pressure of said fluid to decrease said flow rate when thepressure exceeds a predetermined level; and linkage means between saidmember, said manual means and said compensator means for decreasing saidflow rate at varying increments per increment of pressure differentialabove said predetermined level.

11. A concrete pumping apparatus as defined in claim 10, in which saidcompensating means includes an element biased to a first position andmovable from said first position in response to increases in pressure ofsaid fluid; linkage means between said element and said member, saidlinkage means moving said member in progressively increasing incrementsfor each increment of movement of said element from said first position,said manual means cooperating with said linkage means through a lostmotion connection to accommodate relative movement between said linkagemeans and said manual control means when the pressure of the fluidexceeds said predetermined level.

1. In a concrete pumping apparatus having a concrete placement conduit,first and second fluid rams cooperating with said conduit for deliveringmaterial through said conduit, a hydraulic control circuit for supplyingpressured fluid to said rams comprising a pump delivering fluid to saidrams at varying flow rates and pressures, said pump having a memberpositionable to a plurality of positions to adjust the flow rate of saidfluid; automatic compensator means communicating with the outlet of saidpump and having an element positioned as a function of the pressure ofsaid fluid from said pump; and linkage means interconnecting saidelement and member, said linkage means moving said member at varyingincrements per increment of pressure of the fluid as the Pressure offluid is increased.
 2. A concrete pumping apparatus as defined in claim1, in which said compensator means includes a cylinder having saidelement reciprocated therein; and biasing means normally maintainingsaid element in a first position with the pressure of said fluid movingsaid element from said first position.
 3. A concrete pumping apparatusas defined in claim 2, in which said biasing means comprises a springhaving a constant spring rate.
 4. A concrete pumping apparatus asdefined in claim 1, in which said last means includes linkage meansbetween said element and said member.
 5. A concrete pumping apparatus asdefined in claim 4, in which said linkage means includes a bell crankhaving angularly related links with one link cooperating with saidelement and a second link cooperating with said member.
 6. A concretepumping apparatus as defined in claim 5, in which said links definevarying effective moment arms for said element and said member and inwhich the effective moment arm for said element decreases as saidelement is moved from a first position.
 7. A concrete pumping apparatusas defined in claim 1, and further including manual means cooperatingwith said last means for adjusting said member to define a predeterminedflow rate for said fluid.
 8. A concrete pumping apparatus as defined inclaim 7, in which said manual means and said last means includes a lostmotion connection to accommodate relative movement when the pressure offluid exceeds a predetermined level for said predetermined flow rate. 9.A concrete pump as defined in claim 1, in which said last means includesa bell crank pivoted about an axis with a first link cooperating withsaid member and a second link cooperating with said element, said linksbeing arranged to define effective moment arms for said member and saidelement which have a progressively increasing ratio as said element ismoved from a first position.
 10. In a concrete pumping apparatus havinga pair of rams, each cooperating with a piston reciprocated in adelivery line to deliver material to a placement conduit, a hydrauliccontrol circuit including a reservoir; a pump supplying fluid from saidreservoir to said rams, said pump having a member movable to a pluralityof positions to adjust the flow rate of fluid from said pump; manualcontrol means for adjusting said member to set various maximums of flowrate for said pump; compensator means for automatically adjusting saidmember as a function of the pressure of said fluid to decrease said flowrate when the pressure exceeds a predetermined level; and linkage meansbetween said member, said manual means and said compensator means fordecreasing said flow rate at varying increments per increment ofpressure differential above said predetermined level.
 11. A concretepumping apparatus as defined in claim 10, in which said compensatingmeans includes an element biased to a first position and movable fromsaid first position in response to increases in pressure of said fluid;linkage means between said element and said member, said linkage meansmoving said member in progressively increasing increments for eachincrement of movement of said element from said first position, saidmanual means cooperating with said linkage means through a lost motionconnection to accommodate relative movement between said linkage meansand said manual control means when the pressure of the fluid exceedssaid predetermined level.